1. FIELD OF THE INVENTION
The present, invention relates to a method of producing an optical or magneto-optical recording card and a transfer type optical or mangeto-optical recording medium employable for carrying out the method.
In the recent years a number of cards in which various kinds of information are recorded are increasingly put in practical used as ID card, cash card or bank card.
2. DESCRIPTION OF THE PRIOR ART
This kind of card is required to record various kinds of, informations such as data concerning individual person, data concerning a company from which the card is issued or the like data. In the earlier age such informations were recorded using visual characters and symbols and in the later age they were recorded in response to electrical signals which were generated magnetically. However, due to rapid increase in number of card the conventional card is not in position to take adequate measures for preventing data from being falsified and moreover for the current tendency of increased volume of informations.
In view of the current situation as mentioned above a card including an optical recording layer to which the latest optical technology is applied to record informations has been developed in the recent years. This kind of card is called optical recording card.
A hitherto proposed optical recording card 1 has a basic structure as shown in FIGS. 1 and 2. Specifically, it includes an optical recording layer 4 which is interposed between a card base 2 and a transparent protective layer 3 made of transparent plastics and optical reading is carried out from the side of the protective layer 3. It should be noted that in FIG. 2 an adhesive layer is omitted. The optical recording layer 4 comprises an optical reflective layer which has optical reflection faces on which a number of data pits are formed. Reading is achieved with the use of laser beam 9 by detecting data pits each of which has a different optical reflectivity.
In order to produce optical recording cads as mentioned above a variety of technologies have been developed and in the recent years a method of producing optical recording cards with the use of transfer technique has been proposed from the viewpoint of facilitating production of optical recording cards. An example of production technique for producing optical card with the aid of transfer technique is shown in FIG. 9 and a transfer type optical recording medium is used for practicing the production technique.
Specifically, a transfer type optical recording medium 101 comprises a base film 102, a peeling layer 103, a transparent protective layer 3 made of transparent synthetic resin, an optical recording layer 4 and an adhesive layer 104 which are successively superimposed one above another. When an optical card is produced using the transfer type optical recording medium 101, the base film 102 is peeled off together with the parting layer and a card base 2 is adhesively secured to the transfer type optical recording medium 101 to achieve thermal transfer on necessary part, as shown in FIG. 10. Thus, an optical recording card 100 as shown in FIG. 11 is produced.
A method of producing an optical recording card as mentioned above is a known technique as disclosed on an official gazette of Japanese laid-open patent (official gazette of Japanese Laid-Open Patent NO. 58894/1986 issued on the day of Apr. 5, 1985).
The protective layer 3 of the transfer type optical recording medium 101 used for practicing the above-mentioned prior method of producing a conventional optical recording card constitutes an upper layer of the optical recording card 100 in order to protect the optical recording layer 4 from damage or injury and moreover reduce a rate of occurrence of error during data reading. Accordingly, the protective layer 3 is constructed by hard material having a thickness of about 400 microns. However, the fact that the protective layer 3 is constructed by thick and hard material makes it difficult to produce the transfer type optical recording medium 101 in tape-shape which can be wound about a reel. This means that it is inconvenient to handle the transfer type optical recording medium 101 when an optical card is produced.
Further, since the protective layer 3 has a heavy thickness, there is a fear that it is deformed under the effect of heat during thermal transfer and its surface loses smoothness. This leads to a cause that a rate of occurrence of error during data reading increases.
Since laser beam is adapted to pass through the protective layer when data is written in the optical recording layer or data written in the optical recording layer is read, damaged or injured protective layer or contaminated protective layer causes S/N ratio to be reduced.